I just got 3 fillings on my teeth 2 days ago, but it hurts, do i need a root canal?

I went to the dentist 2 days ago to get three fillings. The dentist told me that this one tooth was pretty deep but she got cleaned out and was gOnna fill it. She then told me that if it still hurt that i would need a root canal. It has been irritating me and it hurts to eat on the side where the tooth is at. Do i need to go back and get a root canal or should i just give it time?